This invention relates to the field of cassette-like devices containing photosensitive film.
In accordance with a first prior art approach, a cassette is provided containing a roll of photosensitive media. The film is driven from the cassette by a pair of rollers external to the cassette and within the camera. One problem with this type of approach is that the lead end becomes fogged when the cassette is removed from the industrial camera since the lead end must always be present external of the cassette. Should this not occur, it would be impossible to drive the photosensitive media out of the cassette by means of the external rollers upon subsequent use of the cassette.
Another approach is to provide a pair of rollers within the cassette which are capable of eliminating the above-mentioned problem of fogging as the leader may be driven totally within the cassette and thereafter driven out again. This approach, however, is costly since the rollers, being inside the cassette, are thrown out when the cassette is disposed of upon the exhaustion of the photosensitive media therein.
Furthermore, through the use of both of these approaches, it is possible that the film may be driven by error all the way into the cassette (in the second approach beyond the "bite" of the roller pair) so that the media cannot be thereafter driven out of the cassette to thereby waste the remaining material therein.
It is thus highly desirable to provide a replaceable cassette-like supply device wherein the roller portion associated therewith is preserved for use with subsequent disposable cassette in the interest of economy and the material is not fogged due to the elimination of the extended lead edge.
In accordance with a pending patent application U.S. Ser. No. 611,595, filed Sept. 8, 1975, entitled "Two-Part Photosensitive Media Replaceable Cassette Supply Device" by Daniel H. Robbins, a disposable cassette containing photosensitive material is detachably coupled to a light tight buffer box having a pair of drive rollers therein. This two-part supply device is inserted into an industrial camera. The material is pushed from the disposable cassette through the light tight buffer box into the camera for use therein. If it is desired to replace one type of photosensitive material with another, before the material in the cassette is used up, the photosensitive material extending from the buffer box drive rollers to the cutting station in the camera processor is driven back into the bite of the roller pair so that the leader is not exposed to light entering the buffer box through the buffer box exit orifice when the two-part unit is thereafter removed and replaced with a similar two-part unit bearing a different type of material. When the photosensitive material in any two-part unit becomes exhausted, the reusable buffer box is unfastened from the disposable cassette, and the disposable cassette is thereafter thrown away and the buffer box is reused with a fresh cassette.
It is desirable for the lead edge of the roll of material to maintain a constant location with respect to the cutting knife within the camera so that the first sheet cut has a constant length rather than having a variable length where the first sheet leading edge is long or short of the referencing knife position. In other words, it is desirable to automatically cause the leading edge of the sheet to be positioned at the referencing knife position after insertion of the two-part cassette device into the camera so that a fixed amount of roller rotation of the drive means causes the sheet of the first frame to have a predetermined length. It is also desirable to automatically cause the leader extending from the two-part cassette to be withdrawn a predetermined amount almost into the bite of the buffer box roller pair upon withdrawal of the two-part cassette from the camera.